PCB Global and Landing Areas
PCB shape was traditionally measured at room temperature using shim gauges and a granite flat table. The shadow moiré technique is a far superior approach to measurement of PCB shape. Large area PCB shape can be captured at high speed and temperature without sacrificing measurement resolution, unlike some other optical measurement approaches, like Fringe Projection. Bow and Twist standards can be applied automatically through the Akrometrix software to these global PCB measurements.
With tighter component pitches and tolerances, the warpage of PCB landing areas over temperature is becoming increasingly more critical to quantify. Akrometrix equipment is capable of capturing both global and landing area warpage at high resolution in a single thermal run. Many PCBs are known to exhibit different warpage behavior after exposure to multiple reflows. This makes capturing both global and local landing area in a single thermal run essential. Akrometrix Surface Analysis software can batch process multiple PCB landing areas in a repeatable fashion. Additionally the fast (sub 2 second) acquisition time of Akrometrix systems is beneficial for measurement of thinner PCBs that can change shape quickly.
A PCB global and local 3D surface plot are shown below. The image on the right is only a 4x4mm PCB landing area measured with Fringe Projection.
PCB landing area data can be imported into the Akrometrix Interface Analysis software for comparison with corresponding component warpage over temperature. Having both component and PCB landing area warpage over the same temperature points and temperature profile gives customers the ability to analyze the gaps between PCB and component attach surfaces. Below, on the left, a plot of a component bottom and PCB landing area is shown plotted in the Interface Analysis software. A Gap plot between these two surfaces can also be visualized as shown on the right.